Conventionally tocopherols and ascorbyl palmitate are used in order to protect, for example, oils containing fatty acids having at least one double bond from oxidation.
Catechins are natural substances which occur in nature as plant components. They are hydrogenated flavones. Catechins include, in particular, catechin, epicatechin, gallocatechin and epigallocatechin. In the sense of the present invention, “catechin” or “a catechin” always means a compound selected from the group of catechins. “Catechin” is not the catechin meant in the narrow sense. If the catechin in the narrow sense is meant, then this will be also designated “catechin in the narrow sense”. Catechins occur, for example, in green tea and can be extracted from this. Dried leaves of green tea can contain, for example, 8.5 to 20.6% by weight of catechins. Information on catechins and catechins in green tea may be found, e.g., in Römpp Online, Version 3.0, published by Georg Thieme Verlag, under the headwords “Catechine” [Catechins] and “Tee” [Tea].
Catechins are active antioxidants and also have other beneficial properties. However, catechins are hydrophilic and therefore cannot readily be used as antioxidants in lipophilic media. It is therefore desirable to make catechins available as antioxidants for lipophilic media.
Catechins are highly water soluble but very sparingly oil-soluble antioxidants. Recent scientific studies verify in addition health-promoting properties of catechins such as, e.g., accelerated fat combustion, anticarcinogenic activity etc. The oil insolubility restricts the formulation ability of catechins to aqueous systems which prevents their use as additives for oils or a mixture of oils.
In addition to catechins, polyphenols in general, in particular those having antioxidant properties, are also usable as antioxidants. It is therefore desirable to be able to use not only catechins, but polyphenols in general, as antioxidants in lipophilic media also.
If there were a way to incorporate polyphenols, in particular catechins, in a corresponding amount in a stable manner in oils, not only would the very good antioxidant power of polyphenols be usable for oils, but also the health-promoting activity of polyphenols would be able to be combined with those of oils and/or oil formulations. Preferably, the formulations should be free from short-chain and medium-chain alcohols.
Diterpenes are natural substances having 20 carbon atoms which are made up of four isoprene units. They belong to the terpene group. Compounds designated diterpenes are not only hydrocarbons, but also derivatives of the corresponding hydrocarbons. Phenolic diterpenes are those diterpenes which contain at least one phenolic OH group. Carnosolic acid belongs to the phenolic terpenes.
WO 94/22321 discloses solutions of catechins in nonionic solvents. These solutions can be used as antioxidants in fats and oils. As solvents, in particular nonionic surfactants are disclosed, in particular lecithin and fatty alcohols having 8-18 carbon atoms are disclosed. In example 7, inter alia, also glycerol monooleate is disclosed as solvent. However, this has the disadvantage that catechins are only soluble therein at a low concentration and that frequently cloudy oils are obtained.
KR 2001079020 and JP-A 63135483 likewise disclose lipophilic antioxidants which contain catechins.
The object of the present invention was to provide substances which are usable as lipophilic antioxidants.